01 Rough Idle Then Smooth with No Tach

[Mason The Dev]

Hi Everyone,

 

I've got an 01 Drive-train that's doing a weird thing.

First 5 or so seconds, the truck seems to idles a little high, and a little rough. Then it smooths out and sounds like its running fine, but it has to Tach reading. Completely drops to zero, this is consistent. Every time you shut the truck off and restart it, it does this. The tach even reads, while it does read, seemingly accurate. What else has me confused is when I plug the code reader in and go for a drive looking at live data, it also seems to report proper RPM.

I did a cluster test and it didn't seem to have any issues, so I don't think it's a short with the gauge,

the Cam Position Sensor is new, but I suppose could still be faulty.

ECM is reporting RPM to diagnostics, although I'm not positive this data is coming from the CPS sensor.

PCM wire 8 is also sending constant voltage across the wire.

Here is a video of the issue

[Great work!]

Do you have a delayed wait to start light? If so that could be ECM dying. Does the oil and temp gauges keep working when the Tach quits, they take a while to go to zero if there is a comm fail. Check if the alternator is charging when the tach zeros out use a voltmeter on the battery. ECM is responsible for tach, oil and temp gauge. It also tells the PCM that the engine is running.

[Mason The Dev]

10 minutes ago, Great work! said:

Do you have a delayed wait to start light? If so that could be ECM dying. Does the oil and temp gauges keep working when the Tach quits, they take a while to go to zero if there is a comm fail. Check if the alternator is charging when the tach zeros out use a voltmeter on the battery. ECM is responsible for tach, oil and temp gauge. It also tells the PCM that the engine is running.

Yes sir, everything else seems to work as intended. Truck will run drive and charge for hours without problem. Just seems a little gutless and no tach.

[Great work!]

Should have a fault code then for cam or crank sensor problem. Try a different OBD tool. Try unpluging an engine sensor and make sure your code reader detects it. 

[Mason The Dev]

4 hours ago, Great work! said:

Should have a fault code then for cam or crank sensor problem. Try a different OBD tool. Try unpluging an engine sensor and make sure your code reader detects it. 

it does throw p0336 or whatever it is for camshaft, two different tools tell me the same thing. It’s the only code, just baffled because it’s a new sensor in there. Though I don’t know how quality the part is, I’m going to try a known good one this weekend.

[Mopar1973Man]

Check the wiring it could be wiring issues. Then its possible the tone ring fell off into the pan ive seen one case of this. Poor quality sensor possible.

[dripley]

Did you clear the code after it set and you replaced the sensor?

Edited October 7, 2020 by dripley

[Mason The Dev]

1 hour ago, Mopar1973Man said:

Check the wiring it could be wiring issues. Then its possible the tone ring fell off into the pan ive seen one case of this. Poor quality sensor possible.

wiring seeeeeeems good, RPM is reported to ecm, so I’m thrown off completely, but it’s definitely worth a look. Thanks.

 

1 hour ago, dripley said:

Did you clear the code after it set and you replaced the sensor?

 

Yes sir, of course.

[Mason The Dev]

Okay update. I took a visit to my ol man, and we pulled the sensor that we know is good out of one of his trucks (What a fight that was), and tried it in mine. Same problem! Also put my sensor in his truck and it works fine, so my sensor IS GOOD.

I used one of those little dentist mirrors, like the ones they use to see the back of your teeth, and a flash light to get a look in the whole and the tone ring looked fine to me.

 

What's interesting.... with the sensor unplugged, the tach still works for a few seconds before it conks out...?

So, we checked wires, and voltages are the same across both trucks.

 

So I need a new lead to follow! I read somewhere that if the PCM doesn't get a signal back from the tach, it'll throw it to zero? Maybe that's somewhere to look. 

[jag]

P0336 is a crankshaft sensor code, not the camshaft. Check behind your starter for a crank sensor. I know the 01's are not supposed to, but your truck just might be 1 of the lasts one that snuck bye. The dropping tach is pretty well a sure fire sign as well as funky idle. Looking doesn't cost nothing neither. 

[Mason The Dev]

3 hours ago, jag said:

P0336 is a crankshaft sensor code, not the camshaft. Check behind your starter for a crank sensor. I know the 01's are not supposed to, but your truck just might be 1 of the lasts one that snuck bye. The dropping tach is pretty well a sure fire sign as well as funky idle. Looking doesn't cost nothing neither. 

2001 doesn’t have a crankshaft sensor, but ill double check anything at this point.

 

edit: well I just looked and I can’t see anything that looks even remotely like a sensor. Aahhhhhh

Edited October 12, 2020 by Mason The Dev

[Mason The Dev]

The ECM has an accurate reading of how fast the engine is spinning, so it leads me to believe it's else where.

I think sensors are all good.... cluster test says the cluster is good as well.

[jag]

So what code number is it actually showing on scan tool?

It throws a p0336 or whatever it is for camshaft doesn't really help the Dodge Doctors on here to help cure your problem, just need the correct information.

 

[Mason The Dev]

14 minutes ago, jag said:

So what code number is it actually showing on scan tool?

It throws a p0336 or whatever it is for camshaft doesn't really help the Dodge Doctors on here to help cure your problem, just need the correct information.

 

The code IS for the cam shaft, two different scan tools confirm that. 
 

however it’s not the sensor, mechanically the truck seems to be working just fine. Tested the sensor in another truck and it worked fine and dandy. Live readings give accurate information. I’m gonna pull the cluster out and check grounds and whatnot next

[leety]

3 hours ago, Mason The Dev said:

The code IS for the cam shaft, two different scan tools confirm that. 
 

however it’s not the sensor, mechanically the truck seems to be working just fine. Tested the sensor in another truck and it worked fine and dandy. Live readings give accurate information. I’m gonna pull the cluster out and check grounds and whatnot next

This may sound really dumb and overly simplified but when I first got my truck it was having all sorts of vodo adgeacent, seemingly undiagnosable issues. It was like someone had put a spell on my truck.

 

The remedy?

 

Replace all four of the battery cable ends with military connectors. I used marine heat shrink over the solered eylets to keep things from getting corroded again.  I also replaced the ground wire run that goes between the batteries.  It was full of corrosion. After I did that the throwing of random nonsensical codes and seemingly undiagnosable voodoo issues magically vanished.

 

 

 

Just sayin'

 

 

[jag]

Are you getting any codes from the other module? Plus the first code you got was p???? Kind of hard to figure out what to look for without the proper code thingy. More than 1 code for the camshaft thingy.

[Mason The Dev]

5 hours ago, leety said:

This may sound really dumb and overly simplified but when I first got my truck it was having all sorts of vodo adgeacent, seemingly undiagnosable issues. It was like someone had put a spell on my truck.

 

The remedy?

 

Replace all four of the battery cable ends with military connectors. I used marine heat shrink over the solered eylets to keep things from getting corroded again.  I also replaced the ground wire run that goes between the batteries.  It was full of corrosion. After I did that the throwing of random nonsensical codes and seemingly undiagnosable voodoo issues magically vanished.

 

 

 

Just sayin'

 

 

My battery connectors are pretty crap honestly, I’ll pick some up at Napa when I get over there this week.

 

2 hours ago, jag said:

Are you getting any codes from the other module? Plus the first code you got was p???? Kind of hard to figure out what to look for without the proper code thingy. More than 1 code for the camshaft thingy.

P0336, only code. It’s for the cam sensor. No other codes.

 

Tested the sensor in another truck. It works great.

[dripley]

I suffered thru a period electrical gremlins myself. Seems one would stop and another one pop up. I replace all my battery cables then did WT's ground mod and and it has run flawlessly four 2 years or more. These truck definitely need good clean power to operate.